Oil and gas drill operations, both onshore and offshore, generate drill cuttings that require disposal. In offshore operations, cuttings may be ground up into slurry and re-injected into a waste well for disposal. More commonly, the cuttings are placed in transport boxes or containers and transported to shore for disposal which is usually expensive and time consuming. Onshore, drill cuttings are transported to a designated disposal site where the cuttings may require even additional treatment prior to land farming. Moreover, such onshore operations typically employ a plastic lined earthen reserve pit to temporarily store waste mud and drill solids until final disposal. Unfortunately, in particularly arid areas, a considerable amount of evaporation may occur which could release volatile emissions.
Drill cuttings, are mostly composed of mineral substances found in the ground, mixed with drilling fluid which may contain hydrocarbons, water and various additives. The amount of drill cuttings produced varies depending upon many factors. However, in general, drill operations often produce from one to two cubic meters of drill solids per meter drilled.
With the increase in horizontal drilling for shale plays, oil base mud is becoming more widely used in drilling the horizontal section of the well. Cuttings from such horizontal drilling operations may comprise up to 15% or even more hydrocarbons by volume. In addition, these oil based muds are often emulsified as an invert mud and therefore may also contain 20-30% or more chloride salts in solution such as calcium chloride. Typically, these chloride containing drill cuttings must be remediated for a number of reasons including regulatory reasons prior to disbursing or disposal. That is because unlike hydrocarbons which biodegrade over time chlorides may accumulate in the soil and lead to various environmental contamination issues.
Moreover, even though hydrocarbons may biodegrade over time, higher molecular weight hydrocarbons are usually slower to biodegrade than lower weight compounds. Unfortunately, these higher molecular weight hydrocarbons may reduce the ability of soil to support plant life or a variety of organisms.
For the above reasons, land treatment sites comprising drill cuttings usually must be monitored closely. Specifically, the physical and chemical composition of the waste-soil mixture are monitored, as well as, composition of runoff The frequency and specifics of the monitoring may vary depending upon site topography, hydrology, and
In some cases oil base drill cuttings are subjected to thermal desorption in order to reducing the hydrocarbon content. While the hydrocarbon content may be reduced via thermal sorption, such a treatment generally not address chlorides. Moreover, the process is expensive and has limited throughput, for example, less than two tons per hour in many cases. What's more, regardless which one or combination of the aforementioned methods are employed the cuttings still must be transported to a disposal site which further adds to the cost.
New processes for treatment of drill cuttings are needed. It would be beneficial if such processes reduced both chloride and hydrocarbon content effectively and efficiently. It would further be beneficial if such process reduced and/or eliminated the necessity of land farming or spreading and associated transportation, offshore cuttings transportation, cuttings grinding and re-injection, and the need for a reserve pit. It would be further beneficial if such new processes were capable of recycling water and reduced the need, cost and transport for the next well operations.
Advantageously, the present invention often meets all the aforementioned needs and more. In one embodiment the invention relates to a process for treating drill cuttings from an oil or gas operation. The process comprises first mixing the drill cuttings with an aqueous emulsion comprising one or more oil-liquid membranes surrounding a nano scale compound comprising iron, magnesium, or both. The weight ratio of emulsion to water is from about 1:150 to about 1:3000 while the weight ratio of water to drill cuttings is from about 40:60 to about 70:30. Next, any hydrocarbons may be skimmed and treated drill cuttings may be removed. If desired, water may be oxidized.